Edge design for reducing unwanted photic effects in intraocular lenses

ABSTRACT

An intraocular lens (IOL) has an optic, a peripheral rim, and a reduced thickness region connecting the optic to the peripheral rim. The peripheral rim has a continuously curving outer edge that it does not include any tangents parallel to the optical axis either along its length or at the intersection of the outer edge with the anterior or posterior surfaces of the IOL.

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 14/060,144 filed on Oct. 22, 2013, and claims thepriority of U.S. Provisional Patent Application No. 61/734,261 filed onDec. 6, 2012.

TECHNICAL FIELD

This invention relates generally to the field of intraocular lenses and,more particularly, to an edge design for reducing unwanted photiceffects in intraocular lenses.

BACKGROUND OF THE INVENTION

The human eye in its simplest terms functions to provide vision bytransmitting light through a clear outer portion called the cornea, andfocusing the image by way of a crystalline lens onto a retina. Thequality of the focused image depends on many factors including the sizeand shape of the eye, and the transparency of the cornea and the lens.When age or disease causes the lens to become less transparent, visiondeteriorates because of the diminished light which can be transmitted tothe retina. This deficiency in the lens of the eye is medically known asa cataract. An accepted treatment for this condition is surgical removalof the lens and replacement of the lens function by an artificialintraocular lens (IOL). In the United States, the majority ofcataractous lenses are removed by a surgical technique calledphacoemulsification. During this procedure, an opening is made in theanterior capsule and a thin phacoemulsification cutting tip is insertedinto the diseased lens and ultrasonically vibrated. The vibratingcutting tip liquefies or emulsifies the lens so that the lens may beaspirated out of the eye. The diseased lens, once removed, is replacedby an IOL.

A known difficulty for intraocular lenses has been that off-axis lightrays can be reflected or transmitted into the visual field, producingundesirable photic effects. Edge designs for IOLs have been proposed tosteer the unwanted light rays to different locations, but depending onthe incident angle of the incoming light, this may not address theproblem sufficiently and may inadvertently create new photic effects.The problems may be exacerbated in thin lens designs that use particularedge shapes for mechanical stability. There accordingly remains a needto reduce these undesired photic effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example IOL according to a particular embodimentof the present invention;

FIG. 2 illustrates a cross-sectional view of a particular embodiment ofan IOL with a continuously curving outer edge;

FIG. 3 illustrates a cross-sectional view of another particularembodiment of an IOL with a continuously curving edge having recessedsurfaces; and

FIG. 4 illustrates a cross-sectional view of another particularembodiment of an IOL that includes a flat, anterior-facing surfacemeeting the reduced thickness region.

DETAILED DESCRIPTION

Various embodiments of the present invention provide shaped edges forIOLs to reduce photic effects. In particular embodiments, an anteriorsurface of the IOL is formed with a continuously curving edge thatredirects transmitted and reflected off-axis light to reduce negativevisual effects. In certain embodiments, a continuously curving edge mayalso be employed in conjunction with a thickened periphery to allow forimproved mechanical stability in relatively thin lenses. Further featureand advantages of various embodiments will be apparent from thefollowing detailed description.

Foldable IOL designs using a thickened rim for improved mechanicalstability are disclosed, for example, in U.S. Patent ApplicationPublication No. 2009/0088842, which is incorporated herein by reference.Such designs may include a recessed surface on the anterior and/orposterior face of the lens around an edge of the optic, thereby reducingthe overall bulk of the optic. The recessed surface is in turnsurrounded by the thickened rim attached to the haptics, providingadditional mechanical stability to prevent the optic from buckling ortilting. The interaction between the rim and incoming off-axis lightrays can produce unwanted photic effects that can deteriorate visualquality for the IOL patient. Various embodiments of the presentinvention provide an improved edge design for such IOLs that reducesthese unwanted photic effects.

FIG. 1 illustrates an example IOL 10 according to a particularembodiment of the present invention. IOL 10 is formed from as asingle-piece from a soft, foldable, biocompatible material of any of thenumerous such materials known by those skilled in the art, including bynot limited to silicone, hydrogel and soft acrylic materials that mayalso include compounds to absorb specific wavelength ranges of light(such as ultraviolet light). In the depicted embodiment, IOL 10 includesoptic 12 and haptics 14. Optic 12 refers to the central region of theIOL 10 that is configured to focus incoming light onto the retina toprovide vision to the patient. The optical axis of the optic 12corresponds to the direction of parallel light rays from a distantobject that are focused by the optic 12. The optical surface of theoptic is defined as the region having a base curvature determining theoptical power of the optic, with the outer boundary of this optical zonedefining an edge thickness of the optic (“thickness” in this contextreferring to a thickness along the optical axis). The diameter of theoptical surface is preferably in the range of 4.5-7.0 mm, correspondingto an ordinary range of pupil diameters in patients.

In the depicted embodiment, optic 12 is depicted as a monofocalrefractive optic with a radius of curvature determining the opticalpower of the optic 12. In principle, however, optic 12 could have anysuitable structure for focusing light onto the retina, which may includediffractive or refractive elements. Optic 12 may also include suitablemodifications for correcting monochromatic or chromatic aberrations(including but not limited to spherical aberrations of any order, coma,astigmatism), including such means as toric or aspheric opticalsurfaces. Hence, it should be apparent to one skilled in the art thatany number of known optical designs for IOLs can be included in variousembodiments of the present invention.

IOL 10 is depicted as an IOL typically implanted in the capsular bag,but various embodiments of the present invention could include phakicIOLs placed in the anterior chamber of the eye or sulcus-fixated lensesfor the posterior chamber. Haptics 14 can include any mechanical supportstructure for the IOL that maintains the IOL in place in the appropriateanatomical location. The haptics 14 shown in the depicted embodiment aretypical for placement in the capsular bag, but one skilled in the artwill be aware of numerous other modifications to the depicted structure.The haptics 14 are shown as being formed integrally with the rest of theIOL 10, but they could also be separate pieces attached to the peripheryof the IOL 10.

Rim 30 is a thickened outermost periphery of the IOL 10 integrallyformed with optic 12 that is joined to the haptics 14 and that providesmechanical stability for the optic 12 when the IOL 10 is in place. Therim 30 is connected to a reduced thickness region relative to the edgeof the optical surface (where thickness is measured along the opticalaxis of the IOL 10) that surrounds the optical surface. The rim 30 isthickened relative to this reduced thickness region. In order to providean advantageously thin IOL profile, the rim should have a thickness of0.3 mm or less relative to an expected optic thickness of 0.19 mm-0.45mm with the reduced thickness region being 0.1 mm thick or less.However, depending on the optical power requirements of the lens, muchthicker lenses may be required, so that the rim 30 and the reducedthickness region of the optic 12 could be thicker while still allowingthe optic 12 to remain stable with a relatively smaller thickness thanif the rim 30 were not present.

FIG. 2 shows a cross-sectional view of a particular embodiment of an IOL100 with a continuously curving outer edge, with the cross section takenalong line A-A of FIG. 1. The outer edge 102 faces outwardly from theoptical axis, and it extends between the anterior surface 104 and theposterior surface 106 of the IOL, meeting the respective surfaces 104and 106 at corners, which may be sharp discontinuities or somewhat moregradual reversals of the profile of the surface long the optical axis.The outer edge 102 is “continuously curving,” which is to say that itdoes not include any tangents parallel to the optical axis either alongits length or at the intersection of the outer edge 102 with either ofthe surfaces 104 and 106. In particular embodiments, the radius ofcurvature of the continuously curving outer edge 102 may be constant andrelatively gradual, such as 0.8 mm. In other embodiments, the radius ofcurvature of the continuously curving outer edge may be relativelysteep, such as 1.19 mm. By presenting a relatively large surface area toincoming light without any consistent surface orientation, thecontinuously curving edge thereby prevents any substantial transmissionof off-axis light through the edge to any particular location as well asdistributing internally reflected light away from the fovea of theretina. The combination of these features thus reduced undesired photicphenomena.

Advantageously, the continuously curving edge may also be configured todirect light to particular locations. For example, a first portion ofthe outer edge 102 may have a configuration (orientation and curvature)to reflect internal light rays to a location within the body of theoptic 12, while a second portion of the outer edge 102 may have acurvature such that it reflects incoming light rays outside of, andgenerally posterior to, the body of the optic 12. This combination helpsto redirect off-axis light away from the visual field. Additionally, theouter edge 102 and/or the periphery of the anterior and/or posteriorsurfaces 104 and 106 may be textured, coated, or the like to diffuse orabsorb incoming light to some degree, which can further reduce unwantedphotic effects.

In the depicted embodiment of FIG. 2, the reduced thickness regionaround the optic 12 is formed by a recess in the anterior surface 104outside of the optical surface of the optic 12, while the posteriorsurface 106 has a continuous curvature until the corner at which theposterior surface 106 intersects the outer edge 102. In combination withthe features of the outer edge 102, this facilitates the ability of theouter edge 102 to redirect light away from the visual field. FIG. 3shows an alternative embodiment in which both the anterior surface 108and the posterior surface 110 are both recessed to form the reducedthickness region. Relative to a flat outer edge, the continuouslycurving outer edge 102 will still produce reduced photic effects, butthe recessed posterior surface 110 may tend to direct light rays closerto the fovea, which can make photic effects more significant relative tothe embodiment shown in FIG. 2. However, the continuously curving edgedesign can still provide improved performance under these circumstances.

In the depicted embodiment of FIG. 2, the anterior surface 104 of theIOL meets the peripheral rim 102 at a sharp discontinuity. FIG. 4illustrates an alternative embodiment in which the anterior surface 104of the peripheral rim 102, having the same maximum thickness, includes aflat, anterior-facing surface meeting the reduced thickness region. Asin the case of FIG. 3, there may be additional photic effects associatedwith the flat portion of the anterior surface, such as transmission ofoff-axis light rays, but these effects will nonetheless be mitigated tosome extent by the continuously curving outer edge.

Those having ordinary skill in the art will appreciate that variouschanges can be made to the above embodiments without departing from thescope of the invention.

What is claimed is:
 1. An intraocular lens (IOL) formed from a soft, foldable material, comprising: an optic having an anterior optical surface having a first base curvature and a posterior optical surface having a second base curvature, wherein: a diameter of the posterior optical surface is greater than a diameter of the anterior optical surface; and the first and second base curvatures collectively define an optical power of the optic; and a peripheral rim extending between the anterior optical surface and the posterior optical surface and intersecting each surface at a respective corner, the peripheral rim defining a cross section having a continuously curving outer edge having a constant radius and that does not include any tangents parallel to an optical axis of the optic.
 2. The IOL of claim 1, wherein the first base curvature is the same as the second base curvature.
 3. The IOL of claim 1, wherein the first base curvature is different than the second base curvature.
 4. The IOL of claim 1, wherein the optic is a monofocal refractive optic.
 5. The IOL of claim 1, wherein the optic is toric, aspheric or both.
 6. The IOL of claim 1, wherein at least a portion of the peripheral rim is textured.
 7. The IOL of claim 1, wherein at least a portion of the anterior optical surface is textured.
 8. The IOL of claim 1, wherein at least a portion of the posterior optical surface is textured. 